Add tracing support and detectors

[JLBegin]

Added detectors for sampling volume simulation and more.

Changes

• Support photon tracing by logging photon ID during all interactions.
• Added flat solid Circle and Rectangle.
• Added Solid.asDetector(halfAngle) to convert any solid to a detector.
• Implement detectors (capture inside halfAngle or pass through).
• Implement detectedBy data filters to obtain photon traces that were captured by some detector(s).
• Added example to showcase sampling volume simulation.

Other

• prevent use of vtk 9.5 as it is not yet compatible with mayavi.
• fix rotation bug in GetAxisAngleBetween when orientation changed to opposite direction.
• fix cuboid hash not taking into account its materials
• fix photon batching when nWorkUnits > N
• optimize data export to decrease RAM usage.
• specify test coverage options

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Examples

Any Solid can be used as a detector. A sphere for example (with a wide light source from the left):

Included in the simulation stats:

Report of solid 'detector'
  Detected 2.20% of total power

Future improvements

• Add display/filter options for multi-detectors.
• Allow detectors to be invisible (no capture) or to block rays outside halfAngle.
• Add display endpoints to show photon traces.
• Support filtering data during simulation to minimize memory usage.